Edwards HGM, Jay WH. English delftware (c. 1770) from Bristol, Lancaster and Liverpool: A composition study using Raman spectroscopy and electron microscopy.
Spectrochim Acta A Mol Biomol Spectrosc 2022;
279:121458. [PMID:
35687989 DOI:
10.1016/j.saa.2022.121458]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Revised: 05/28/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
Nine decorated lead-tin glazed earthenwares, colloquially termed 'delftware', produced in c. 1770 in Bristol, Lancaster and Liverpool, England, have been analysed non-invasively by Raman spectroscopy and electron microscopy. The body paste used to manufacture these west coast wares was attained by the blending of highly dolomitic [CaMg(CO3)2] "blue" clay sourced from Carrickfergus, County Antrim, Ireland, with locally sourced clays. Thus, the resulting body fabric of these wares contains significant MgO enabling them to be differentiated from MgO-free London manufactured delftware. The glazes employed all contain arsenic, obtained as a cobalt impurity or by deliberate addition. The presence of this unvolatilised arsenic in the glaze has then reacted with the lead during firing at temperatures approaching 1000 °C and then further reacted with calcium and magnesium to form needle-like crystals of lead arsenates in the form of mimetite [Pb5(AsO4)(Cl,OH)], schulténite [Pb(AsO3OH)], β-roselite [Ca2Co(AsO4)2·2H2O], hedyphane [Ca2Pb3(AsO4)3Cl], wendwilsonite [Ca2Mg(AsO4)2·2H2O] and/or adelite [CaMgAsO4(OH)] during high temperature firing.
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